The present invention relates to a metal cylinder head gasket with compressibility adjusting slits to adjust a surface pressure of a bead.
A cylinder head gasket is situated between a cylinder head and a cylinder block to securely seal therebetween. In case the cylinder head gasket is made of a metal plate or plates, in order to provide a surface pressure around a cylinder bore for securely sealing around the cylinder bore, a bead is generally formed around the cylinder bore.
On the other hand, recently, an engine has been developed to become compact and have a light weight. Therefore, the space between the cylinder bores is gradually made narrower. For this engine, also, the gasket has to securely seal around the cylinder bores.
In case the beads are formed to completely surround the cylinder bores in the engine with the narrow space between the cylinder bores, even if bolts are tightened to securely seal around the cylinder bores, the beads may not be completely compressed due to the various factors, such as compressibility of the bead, rigidity of the cylinder head or cylinder block, and so on.
In this case, a slit may be formed outside the bead to partly surround the same to thereby control the compressibility of the bead. However, in case the slit is simply formed around the bead, the bead may be relatively easily compressed, but the bead may not properly seal around the cylinder bore.
The present invention has been made in view of the above, and an object of the invention is to provide a metal cylinder head gasket with a bead, wherein rigidity of the bead can be partly controlled to thereby improve the tightening ability of the cylinder head.
Another object of the invention is to provide a metal cylinder head gasket as stated above, wherein the bead can be properly compressed to securely seal around the cylinder bore.
Further objects and advantages of the invention will be apparent from the following description of the invention.
A metal cylinder head gasket of the invention is used for an internal combustion engine, and is basically formed of a metal plate extending substantially throughout an entire area to be sealed. The gasket includes a plurality of first holes for cylinder bores situated in the metal plate, a plurality of second holes for bolts situated in the metal plate, and a plurality of beads formed in the metal plate to be situated around the first holes for sealing around the same. An intermediate area is situated between two of the plurality of first holes situated adjacent to each other. Also, a plurality of slits is formed in the metal plate to partly surround the beads between the second holes except for the intermediate area.
In the invention, each slit includes narrow and wide areas. The narrow area has a width narrower than that of the wide area to adjust compressibility of the bead to thereby securely seal around the first holes. In comparing the compressibility at the narrow and wide areas, the bead portion near the wide area can be relatively easily compressed than that near the narrow area.
In the invention, since the slit has the narrow and wide areas, although the bead is formed constantly on the metal plate, the compressibility of the bead can be adjusted easily. Thus, the bead can be compressed equally according to the rigidity of the cylinder head.
Each slit includes an outer edge extending substantially along the bead situated adjacent thereto, and an inner edge with steps to form the narrow and wide areas. The outer and inner edges are curved along the bead. Also, the wide area extends toward the bead from the narrow area.
Two narrow areas are located close to the second holes and sandwich the wide area. This form is suitable for a cylinder head with a high rigidity. Namely, since the rigidity of the cylinder head is high, when the cylinder head is tightened, the cylinder head is compressed generally flat without bending upwardly at the middle area between the bolt holes. In this case, the areas near the bolt holes are compressed strongly, so that the wide area is located between the narrow areas.
Two wide areas may be located close to the second holes and sandwich the narrow area. This form is suitable for a cylinder head with a low rigidity. Namely, since the rigidity of the cylinder head is low, when the cylinder head is tightened, the cylinder head is not compressed flat, i.e. an area between the bolt holes is slightly bent upwardly. In this case, if the areas near the bolt holes are compressed strongly, the area between the bolts holes is bent upwardly, so that the wide areas are formed near the bolt holes to allow the bead to bend more easily near the bolt holes. As a result, the bead can be bent generally equally.
The first holes are generally arranged linearly in a longitudinal direction of the gasket. In this case, the slits are formed to sandwich the first holes therebetween generally along the longitudinal direction.